1. Field of the Invention
The present invention relates to a film transport device of a camera, and more particularly, to a film transport device of a camera in which a film patrone housing a leading end of a film therein is loaded.
2. Description of the Related Art
There has recently been invented a film patrone in which an initial feed-out operation of the leading end of a film housed therein is performed when it is loaded in a camera. In a camera used with such a film patrone loaded therein, various suggestions have been made about a film transport device which feeds out, winds and rewinds a film, wound on a spool shaft in the film patrone, out of the film patrone by forwardly and backwardly rotating the spool shaft by the driving force of a drive motor.
For example, a film transport device of a camera disclosed in Japanese Laid-Open Patent Application No. 96321 of 1982 winds and rewinds a film with two one-way clutches respectively disposed in a driving portion on the side of a spool shaft in a film patrone and a driving portion on the side of a film wind spool in order to stably transport the film by rotating the spool shaft in the film feed-out direction.
In a film transport mechanism of a camera disclosed in Japanese Laid-Open Patent Application No. 67534 of 1990, an engaging shaft having a fork portion to be engaged with a film supply spool in a film patrone and a film wind spool are simultaneously driven, the peripheral speed difference between a film feed-out operation and a film wind operation, which is caused by the start of the film wind operation by the film wind spool after the film feed-out operation, is absorbed by a one-way clutch disposed on the side of the fork portion, and, when the film is rewound, the rotational driving force is not transmitted through this one-way clutch, but through a train of gears to the fork portion engaged with the film supply spool in the film patrone.
Although the above-mentioned peripheral speed difference is determined by the diameter of the film wind spool, the diameter of the spool in the film patrone, the reduction ratio of a film wind driving system, the reduction ratio of a film feed-out driving system and the like, the film wind speed is set to be higher than the film feed-out speed in order to increase the number of exposures per second and to perform an initial film feed-out operation with reliability.
A film transport device of a camera disclosed in Japanese Laid-Open Patent Application No. 67535 of 1990 is provided with a switching means, comprising two one-way clutches and a train of planetary gears, to switch the transmission of the driving force to a patrone shaft by changing the rotating direction of a drive motor, thereby feeding out, winding and rewinding the film.
In this case, the reduction ratio on the rewind side is higher than that on the wind side, by which one of the one-way clutches does not transmit the rotation for rewinding to a film wind spool. Since the reduction ratio of the gears for feeding the film out is higher than that on the wind side, when the film is fed out and wound on the wind spool, the other one-way clutch for transmitting the driving force on the feed-out side is freed as the rotating speed of the wind spool is high.
However, since the film transport device disclosed in the above Japanese Laid-Open Patent Application No. 96321 of 1982 uses one-way clutches, it is difficult to transmit the driving force when the clutches are acting, and when the film wound on the spool shaft in the film patrone is fed out and wound, the wind diameter of the film is decreased in the film patrone. When the film feed-out resistance is increased, the film wind operation is not performed smoothly.
Furthermore, in the film transport device disclosed in the above Japanese Laid-Open Patent Application No. 67534 of 1990, since the train of gears for transmitting the rotating force of a drive motor to the fork portion needs two transmission systems respectively for feeding out and rewinding the film, the film transport mechanism is complicated and the number of components is large. Therefore, the space occupied by the film transport mechanism itself is enlarged.
Still furthermore, in the film transport device disclosed in the above Japanese Laid-Open Patent Application No. 67535 of 1990, since the difference in reduction ratio between the film rewind mechanism and the film feed-out mechanism is a limitation in design, the reduction ratios thereof cannot be set at the same value in order to reduce the number of gears and downsize the mechanisms.
Since the devices disclosed in the above Japanese Laid-Open Patent Applications Nos. 67534 of 1990 and 67535 of 1990 use one-way clutches in the same manner as the device disclosed in the above Japanese Laid-Open Patent Application No. 96321 of 1982, they have the same problem that the film wind operation is not performed smoothly.